In recent years, there have been proposed and developed various valve timing control devices, configured to realize a so-called “Atkinson cycle” by controlling intake-valve timing to an angular phase retarded from an intermediate phase between a maximum phase-retard position and a maximum phase-advance position when starting an internal combustion engine from cold, thus creating an expansion ratio higher than an effective compression ratio.
However, in a hybrid electric vehicle (HEV) or an idling-stop system equipped automotive vehicle, in which an internal combustion engine can be automatically stopped without any driver's intention, the vehicle is restarted usually under a high engine temperature condition. Thus, it is necessary to restart the engine at the valve timing, retarded with respect to the intermediate phase suited for cold-engine starting.
Hence, Japanese Patent Provisional Publication No. 2010-195308 (hereinafter is referred to as “JP2010-195308”) teaches a controller for a hybrid vehicle employing a variable valve timing control (VTC) device, configured to hold the valve timing at an intermediate phase so as to ensure a good startability during engine cold-start operation where the engine is started by manually turning an ignition switch ON, and also configured to hold the valve timing at an angular phase retarded from the intermediate phase so as to reduce noise and vibrations of the engine during automatic engine restart operation.